1. Field of the Invention
The invention relates to a method of reducing torque loading on a system driven by an electric motor and producing cyclically occurring, rotational speed-dependent load-torque fluctuations. Furthermore, the invention relates to a device for performing the method.
2. Description of the Related Art
A method is known from German Published Non-Prosecuted Application No. (DE-OS) 35 40 645 which has as its object the creation of a device which ensures the damping of torsional vibrations in a multi-mass torsional vibrator with an active system. Such torsional vibrations occur predominantly where fluctuations in torque are produced due to different load torques. These fluctuations in torque may excite vibrations, which will lead to very high dynamic loadings of the components in a system wherein several different masses are being moved.
Printing presses, in particular, have a multiplicity of devices which produce different load torques. Thus, for example, gripper controls via cam discs, sheet-feeding devices and sheet-transfer devices, as well as the printing forces themselves, produce cyclically recurring load torques, all of which act upon a central drive. This effect upon the central drive, which also serves to effect the angular coordination of the printing units in addition to the drive, causes elastic deformations in the power transmission means, for example, in the gear train, which likewise occur periodically in accordance with the fluctuations in load torque. The angular coordination and synchronization, respectively, of the individual printing units is thus disrupted, a fact which may become noticeable as register errors in the printed image.
According to the aforementioned heretofore-known method, torsional vibrations which are produced by such fluctuations in load torque are compensated for by torques acting in the opposite direction. Such oppositely directed torques are applied via a control or correcting element and act at a given location within the drive system. This method has a disadvantage, however, in that the counter-torques are produced at a single location in the drive system and thus do not counteract the load torques at the locations at which they are generated. Internal stresses which cannot be compensated for consequently occur within the drive train. These internal stresses within the drive do not reduce the loading on the transmission or gear train but may, under certain conditions, however, further increase that loading and may result in major deformations of the gear train. It is accordingly an object of the invention to provide a method of the foregoing general type which effectively reduces the fluctuations in load torque and which considerably decreases the loading on the drive.